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The mkiv Supra Owners Club

Question about engine issue


Guest kyuss

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Hey there. I have a 2jz motor running a billet 6765 and 18psi on pump gas. I just bent a rod in cylinder #2 and the bottom of the piston skirt hit the crank..or so I was told. What could cause something like this to happen? Top of piston is fine and cylinder walls are fine. Thanks for any help.

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Thanks much. I have been told that 90% of the time when this happens it is due to a mechanical over-rev or mis-shift. That did not happen in this situation so am trying to figure out what else might have been the cause. Thanks again.

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how would a mis shift possible casue a rod to bend?

 

I have no idea, that is why I posted on here. I was told that a "money shift" causes this problem 90% of the time. I can't find any proof of that claim anywhere. So, figured I would ask. Thanks.

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Over rev would fret the rod bolts and pick up a main bearing, or even snap a bolt. The force from overrevving is in the opposite direction to that needed to bend a rod, so it's certainly not that. You need to think about compressive forces, like det or hydraulicing, or even something mechanical like a valve dropping. As you say you've got clean pistons, it's not det or mechanical :shrug:

 

Have you got any pictures of the damage?

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Over rev would fret the rod bolts and pick up a main bearing, or even snap a bolt. The force from overrevving is in the opposite direction to that needed to bend a rod, so it's certainly not that. You need to think about compressive forces, like det or hydraulicing, or even something mechanical like a valve dropping. As you say you've got clean pistons, it's not det or mechanical :shrug:

 

Have you got any pictures of the damage?

 

Thank you for the information. I only have pictures of the top of the pistons and cylinder walls. I will post those up shortly. Again, I really appreciate the help, I am not the most mechanical of sorts.

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